In various industrial materials, there is a case where retention of the temperature during storage or transport is required for maintaining quality and workability. For example, the asphalt mixture is significantly lowered in a workability when the temperature is lowered. Therefore, a temperature decrease is required to be minimized when the asphalt mixture is transported from a manufacturing site such as a plant to a building site such as a construction site by a truck. Generally, in the related art, countermeasures such as covering with two general-purpose sheets for use in a truck bed in an overlapped manner or spreading a felt sheet under the asphalt mixture have been taken.
However, these countermeasures have problems that a sufficient thermal insulation ability cannot be obtained even though two general purpose sheets are overlapped, and that the felt sheet absorbs water and further lowers the temperature of the asphalt mixture. Accordingly, the present inventor has invented an asphalt thermal insulating sheet having a high thermal insulation ability as described in Patent Literature 1. The asphalt thermal insulating sheet is a laminate sheet composed of four sheets. The four sheets comprise a sheet formed of a tarpaulin cloth, a sheet formed of a polyester canvas, both having a rectangular shape and overlapped with each other, and two sheets formed of polypropylene having a width narrower than the above-described two sheets and being interposed therebetween. The sheet formed of the tarpaulin cloth and the sheet formed of the polyester canvas of the laminate sheet are heat sealed along two long sides thereof, while one of short sides of the laminated four sheets is stitched together and the other short side is stitched or heat sealed together.